Lipid peroxidation triggered by the degradation of xCT contributes to gasdermin D-mediated pyroptosis in COPD

Abstract

Pyroptosis is an inflammatory form of regulated necrosis that has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the role of lipid peroxidation in pyroptosis and its underlying mechanisms in COPD remain unclear. In vitro, human bronchial epithelial cells (Beas-2b cells) were exposed to cigarette smoke extract (CSE) for 24 h. In vivo, mice were exposed to cigarette smoke (CS) for 4 weeks. To investigate the role of xCT, we used siRNA and AAV6 to conditionally knock down xCT in vitro and in vivo, respectively. The administration of ferrostatin-1 (Fer-1), a ferroptosis inhibitor that inhibits lipid peroxidation, significantly reduced the cytotoxicity of CSE to Beas-2b cells and mitigated inflammatory exudation, lung injury and mucus hypersecretion in mice with CS-induced COPD. Fer-1 suppressed gasdermin D (GSDMD)-mediated pyroptosis caused by CS in vitro and in vivo. However, in Beas-2b cells and the lung epithelial cells of mice, conditional knockdown of xCT (a negative regulatory factor of lipid peroxidation) inhibited the xCT/GPx4 axis, leading to more severe lipid peroxidation and GSDMD-mediated pyroptosis during cigarette smoke exposure. Moreover, we found that CS promoted the degradation of xCT through the ubiquitin proteasome system (UPS) and that treatment with MG132 significantly inhibited the degradation of xCT and downregulated the expression of pyroptosis-related proteins. The results of this study suggested that the ubiquitination-mediated degradation of xCT drives GSDMD-mediated pyroptosis in COPD and is a potential therapeutic target for COPD. Cigarette smoke induced lipid peroxidation and pyroptosis through the ubiquitination and degradation of xCT. (A) Lipid peroxidation due to the suppression of the xCT/GPX4 axis facilitated pyroptosis in cigarette smoke-induced COPD. (B) The process of xCT protein ubiquitination. In an ATP-dependent manner, Ub is attached to the ubiquitin-activating enzyme E1 and then delivered to the ubiquitin-binding enzyme E2. Next, the E3 ligase acts as a bridge, identifying E2-Ub and the substrate xCT to facilitate the binding of Ub to xCT. Finally, the ubiquitin chain is identified by the 26S proteasome, leading to the degradation of xCT. • In addition to ferroptosis, lipid peroxidation could trigger pyroptosis in COPD. • xCT deficiency exacerbated pyroptosis in cigarette smoke-exposed airway epithelial cells. • Cigarette smoke could promote the degradation of xCT through the ubiquitin proteasome system. • Inhibiting xCT degradation might be an effective treatment strategy for COPD.

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